Process for the absorption of hydrogen sulfide and ammonia from gases



March 3, 1931. c. HANSEN PROCESS FOR THE ABSORPT EON OF HYDROGEN SULFIDEAND AMMONIA FROM GASES Filed June 18,

329%@ @VCO/m1 I sulfite-bisulte solution (prepared Patented Mar. 3,1.931 p y so STATES' enamoran g imam NSEM, or wrnsnonr-oN-TEE-Itmirn,GERMANY, AAssreivon To r. e. AnnnNmn'osrarn AxTmNeEsELLscHAr'r, orraANxFoar-oN-rHE-MAJN, enny Incense ron. TEEABsoBr'rIoN or HYDROGENsunrrnn AND vAMMONIA FaoM eAsEs Application'led June 18, 1927, SerialNo.

The lpresent invention concerns the removal of ammonia and h drogensulfide from `coal gases by washing t e gases, after separation of apart or the whole of the ammonia, in two stages, in such a manner thathydrogen sulfide is precipitated in the form of sulfur in the firststage to the extent that the remainder of the 'hydrogen sulfide ca beab#y sorbed by meansv of a neutral a onium om the' separated ammonia andthe precipitated sulfur). .The absorption of the hydrogen suli fide inthe first stage is effected by washing the gas with the wash-liquorcontaining thiosulfate and polyttionate produced in the second stage,ifnecessar with the'addition of sulfurous acid. The process isdiagrammatl- -cally illustrated by the accompanying flowsheet and may becarried out wholly or in part under increased pressure. y

In accordance with the process described in the application Ser. No.153,452, filed Dec. 8, 1926, the vammonia and hydrogen sulfide containedin coal gases are removed by means of ammonium sulfite-bisulte solutionscontaining certain proportions of ammonia and )sulfurous acid. With thismolecular ratio of l\lI-I3:SO2 the solutions have in fact no tensioneither of ammonia or sulfurous acid, so

'30 that no loss of ammonia/or sulfurous acid occurs. On treating thesesolutions with hyv .drogen sulfide a wash liquor is obtained con-,taining principally ammonium thiosulfate fand ammonium polythionate.This solution may bestill furtherenriched in ammonium polythonatecontent by the addition of sulfurous acid Y 2(NH4)2S2O3+3SO2= and thenboiled in the known manner to give ammonium sulfate and sulfur It hasbeen found however, that the-carry ing out of this' process -is notpractical commercially with the quantities of ammonia 199,862, andan'Germany July 21, 1526.

and sulfuriocdirring in some coal gases, since for the'absorption ofeach molecule of hydrogen sulfide more than four molecules of arnmoniaand a corresponding quantity of sulfurous acid are necessary. The'use ofsuch quantities of' ammonia and sulfurous acid is not a practicableproposition.

The present invention makes possiblethe use of the said neutral ammoniumsulfite-bisulfite solutions for the complete purification of coal gasesfrom ammonia and hydrogenl sulfide. v

rIhe solutions containing thiosulfate and polythionate, obtained inwashing the. gas with sullite-bisulfite solution, also absorb,

without the addition of ammonia, further considerable quantities ofhydrogen sulfide due to the decomposition of the latter with ammoniumpolythionate (uumsioasuzs (NHozsgoaJf-seesngo In the first stage part ofthe hydrogen suly fide is washed out and obtained as sulfur by means ofthe thiosulfate and polythionate solution produced in the second stage.The remainder of the hydrogen sulfide is then absorbed b means of aneutral ammonium sulfite-bisu fite solution produced from the ammoniapreviously se aratedand sulfurous acid. The quantity o hydrogen sulfideto be removed inthe first stage must be such vthat the separated ammoniasuices for remiving the remainder of the hydrogen sulfi e.

In the first stage of the washing a quantity of4 sulfurous acidcorresponding to the hydrogen sulfide may be added'to the washingliquors' or to the gas beforejt 1s introduced polythionate:

into the washing apparatus, so that the washing` process 'proceedsmainly 1n accordance with the equation z---fy l messersoznzolfaS`Thisireaction is `considerably facilitated by the presence of theammonium thiosulfatev contained in the solution. The sulfuro'us acidlnot converted in yaccordance with the above equation combines withthiosulfate to form verted by boiling into ammonium sulfate and sulfur.The sulfur precipitated on boiling and in the rst stage serves for theproduc tion of qthe required sulfur-ous acid The production of thesulte-bisul-fite solution -is advantageously carried outin a separateapparatus but it can, however, be eEected 1n the second stageitself.rllhe process maybe carried out wholly or in part under Superfatmospheric pressure.

I claim:V 4 l. In the processof separating ammonia and hydrogen sulfidefrom gases containing the same b washing the gases with liquors,

the stepsw ich comprise separating from the lgases the greatest part oftheir lanimoma content'by 'causing precipitation of the ammoma by meansolf-water, washingthe residi present in the gases.

` my hand.

ual gases in two stag'es whereby in the first 'stage with the aid ofla-solutiongontaining ammonium thiosulfate, sulfur ldioxide and ammoniumpolythionate such a part ofv thehydrogen sulfide is precipitated inr theform yof sulfur that for the washing of the residual -hydrogen sulfidein the second stage the neuj tral ammonium sulte-bisulfite solutionsufc'es\which is produced from the separated ammonia and sulfur.4

' 2. Process according to claiml l which comt prises-adding to the firstwashing. stage such a p art of sulfurous acid. as is chemicallyequivalent to the amount of hydrogen sulfide 3. Process according toclaim 1 consisting in eecting` the separation of ammonia and hydrogensulfide under superatmospheric' pressure. l y

'4., Process according to claim 1 which com'- a part of sulfurous acidas is chemically process under superatmospheric pressure.

In testimony whereof l have hereunto set A prises adding to the first4washing1 stagesuch equivalent to the amount of hydrogen sulde .present1n the gases, and carrying out the cierran mensen.

